@DaveyCraney You don't mention what device/OS you're using. On an iPad I use iA Writer and Shortcuts. Shortcuts is used to set image size and format save the file and copy the needed text. I then paste that into my iA Writer document and add my alt text.
iA Writer has a feature to publish to Micro.blog. When I'm ready to publish I just hit the button and all the images are uploaded and the post is published to a draft and the website is opened to that draft. I give it a look over, add categories and publish. This would also work on a Mac.